In hospitals, it is frequently necessary to transfer a patient onto or off of the mattress on a mobile stretcher. This is normally done by placing the stretcher in a side by side relationship with another stretcher or a bed, vertically adjusting the stretcher's mattress support frame so that the top of the mattress is at about the same level as the mattress of the bed or the other stretcher, and then sliding the patient transversely onto or off of the stretcher. Moving relatively heavy patients in this manner is one of the most common cause of back injuries to hospital personnel. Therefore, in order to minimize the risk of injury to hospital personnel, it is desirable that the top surface of hospital mattresses present minimal frictional resistance to transverse sliding movement of a patient. On the other hand, simply using a low friction material for the top surface of the mattress would present other problems.
More specifically, the bed frame of hospital stretchers is usually constructed so that it can be moved to positions in which all or a portion of the mattress is inclined, for example a position in which a portion of the mattress is inclined so that the patient is in a sitting position, or a position in which the entire mattress is approximately uniformly inclined so that the patient's head is lower than his feet or his feet are lower than his head. If all or a portion of the mattress is inclined, there would be a tendency for the patient to slide lengthwise on the mattress, and possibly even off the mattress. Obviously, if the patient slides off the mattress head first, the patient could be seriously injured.
Consequently, there are directly competing criteria with respect to the desirable characteristics for the top surface of the mattress. On the one hand, it is desirable that the surface have a low coefficient of friction to facilitate lateral sliding transfers of patients transversely onto and off of the mattress, but on the other hand it is desirable that the surface have a relatively high coefficient of friction so that there will be little or no tendency for a patient to slide lengthwise on the mattress when the mattress is intentionally inclined for medical reasons. Trying to simultaneously satisfy these directly competing criteria has been a long-standing problem for persons designing mattresses for use on hospital stretchers.
It is therefore an object of the present invention to provide a mattress which facilitates transverse sliding of a patient onto and off of the mattress but which resists sliding of the patient lengthwise of the mattress.
It is a further object of the invention to provide such a mattress which can easily be thoroughly cleaned.
Yet another object of the invention is to provide such a mattress which is relatively inexpensive, but which is durable and will experience no significant degradation in operational performance over a relatively long lifetime of use.